1. Field of the Invention
The present invention is related to a system and method for separation of loose granular substrates, and more particularly, to pneumatic vacuum separation of loose materials.
2. Description of the Related Art
Separation of loose granular materials with different densities has been used in variety of industries, such as, coal or gold mining, construction, chemical production, food, agricultural processing and metal industries. It can be used for preliminary and final coal production, ferrous, non-ferrous and noble metals processing, metal slag separation, non-metallic materials separation, separation of food products, industrial and domestic wastes, etc.
A machine for separation of materials with different density is disclosed in French Patent Application No. 2326989, published on Oct. 6, 1975. This system has a separation chamber with an inlet feeder, a cascade of angled surfaces with slots between them, through which pressurized air is supplied from the bottom and sucked in together with small particles from the top of the separation chamber.
The disclosed system has several essential shortcomings. Direction of the separating air flow is from the bottom to the top. The air flow goes through an entire layer of the material, and separation effect requires intensive air flow with considerable pressure (more than 1500 kg/m). Mutual screening of particles does not allow for good efficiency of the process and separation of the material particles with a clear size definition. The system is designed mostly for dust removal.
Another conventional system is a pneumatic separation plant (Russian Patent No. 2282503, Aug. 27, 2006) consisting of a loading bin, a feeder, an air-permeable conveyor belt and nozzles located over the conveyor track and adjusted for separation of the primary material into particles of specific density. The system also includes separating chambers and a suction device for the nozzles. The system also has cyclones and a filter. The nozzles are located at different height from the conveyor belt. The suction device is implemented as a ventilation plant. The shortcoming of this system is inability to regulate technological parameters of separation process by regulating the parameters of suction devices.
Another solution (Russian Utility Model Patent RF No. 78703, 2006) is a pneumatic separation plant consisting of a loading bin, a feeder, an air-permeable conveyor belt, and nozzles located over the conveyor track. The nozzles are adjusted for separation of the primary material into particles of specific density. The system also includes separating chambers, duct collecting system, as well as, suction device for the nozzles. The feeder allows for uniform supply of the primary material to the conveyor belt.
All the nozzles are located at the same distance from the conveyor belt, which ensures free flow of the separated particles. The nozzles are located along the air-permeable conveyor belt at a distance that excludes influences of air flows on the separation process from the nearby nozzles. The nozzles can be moved in a vertical plane. A collector of every nozzle is dead-ended from one side and is connected to the separation chamber from the other side. The separating chamber is connected to the suction device through the dust collecting system.
The shortcoming of this plant is adhesion of fine dispersed particles to the sides of nozzles, horizontal pipes, and round separating chambers. This changes dimensions of the cross section and the basic technological parameters of separation, causing decreased efficiency and production losses. The structure of the plant does not allow for changing the height of the nozzle over the mesh. This makes the process of precise density separation impossible, because the nozzle edge is fixed over the mesh and the air flow affects different size particles unequally. The structure of the plant does not allow to separate plate-shape material, which affects the quality of the recovered product particles.
Accordingly, a particle separation system that improves the quality of separated product particles is desired. Such a system should increase the capacity of a single unit as well as the service and technological reliability.